Multilevel pulse transmission systems employing codes having three or more alphabets

ABSTRACT

A binary pulse signal is converted for transmission into a pulse signal having N possible levels in accordance with a code having three or more alphabets with the input signal first divided into words of predetermined length and the words then encoded in accordance with each alphabet in accordance with the state of the transmitted signal at the conclusion of the transmission of the preceding word.

I United States Patent 1 1 3,587,088

[72] Inventor Peter A. Franaszek [56] References Cited 2 2" UNITED STATES PATENTS [21] P 6 3,233,236 2/1966 Katzenstein m1 340/347 221 Filed De.2l, I967 2,947,804 8/1960 Ellersetal........... 325/32X [45] Paemed 3 369 229 2/1968 Dorros 325/38 x [73] Assignee Bell Telephone Laboratories, Incorporated Mum Hi" Berkeley Hei ms NJ 3,411,089 11/1968 G1cca.... 178/22X y g 3,414,677 12/1968 Quinlan 325/38 X Primary Examiner-Maynard R. Wilbur 541 MULTILEVEL PULSE TRANSMISSION SYSTEMS 'fi EMPLOYNG CODES HAVING THREE OR MORE Attorneys- J. Guent er an W. A arns, Jr. ALPHABETS 4 2s Dr'wmg ABSTRACT: A binary pulse signal is converted for transmis- [52] US. Cl 340/347, sion into a pulse signal having N possible levels in accordance 3325/38 with a code having three or more alphabets with the input [5 1 1 Int. Cl ..H03kl3/24, signal first divided into words of predetermined length and the H041 3/00 words then encoded in accordance with each alphabet in ac- [50] Field of Surch 340/347 cordance with the state of the transmitted signal at the conclu- DD; 325/38, 38 A, 39, 41, 139, 32; 178/22 sion of the transmission of the preceding word. 4 v

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1. Apparatus for converting binary signals into pulse signals having a plurality of possible signal levels greater than two comprising, in combination, means to divide the binary pulse signals into words of a plurality of bits, means to convert said binary words into multilevel signals in accordance with a first alphabet of a predetermined code, means to meaSure a predetermined characteristic of said multilevel signals, means to convert said binary words into multilevel signals in accordance with a second predetermined code alphabet when said measuring means indicates the occurrence of a first predetermined measure of said predetermined characteristic, means to convert said binary words into multilevel signals in accordance with a third predetermined code alphabet when said measuring means indicates that occurrence of a second predetermined measure of said predetermined characteristics, means responsive to the occurrence of predetermined binary words at the output of said dividing means when said measuring means indicates the occurrence of a predetermined one of said predetermined measures of said predetermined characteristics to inhibit said conversion of binary words into multilevel signals until a following binary word is produced by said dividing means, and means to encode said two binary words into multilevel signals.
 2. Apparatus in accordance with claim 1 wherein said binary pulse signals are divided into words of four bits and said three code alphabets are:
 3. Apparatus for converting binary signals into pulse signals having a plurality of possible signal levels greater than two comprising, in combination, means to divide the binary pulse signals into words of four bits, means to convert said binary words into multilevel signals in accordance with a first alphabet of a predetermined code, means to measure the direct current level of said multilevel signals, means to convert said binary words into multilevel signals in accordance with a second predetermined code alphabet when the direct current level of said multilevel signal is at a first predetermined level, means to convert said binary words into multilevel signals in accordance with a third predetermined code alphabet when the direct current level of said multilevel signal is at a second predetermined level, said four bit words of binary pulse signals and said three code alphabets being as follows:
 4. Apparatus for converting binary signals into pulse signals having a plurality of possible signal levels greater than two comprising, in combination, means to divide the binary pulse signals into words of three bits, means to convert said binary words into multilevel signals in accordance with a first alphabet of a predetermined code, means to measure the direct current level of said multilevel signals, means to convert said binary words into multilevel signals in accordance with a second predetermined code alphabet when the direct current level of said multilevel signal is at a first predetermined level, means to convert said binary words into multilevel signals in accordance with a third predetermined code alphabet when the direct current level of said multilevel signal is at a second predetermined level, said three bit words of binary pulse signals and said three code alphabets being as follows: 